Abstract
Oscillating technique is applied into the axial forging process of spline shaft to decrease the forming load and improve the quality of products. A floating axial holder with dwell force is designed to control the material flow. The influences of the floating axial holder have been analysed by finite element (FE) simulation and then verified by experiments. A FE model that considers material property change, elastic recovery and elastoplastic friction was built. The constitutive material model, which is mainly composed of variable elastic modulus and rate-dependent hardening, was used to simulate changes in material properties. Results showed that material flow was improved by decreasing dwell force. Tooth shape can be controlled by changing the dwell force of floating axial holder. The nonlinear function between addendum circle diameter and dwell force has been found. Hence, an optimal value of dwell force was determined considering the forming force, forming defects and tooth shape. Based on the simulating results, the optimal and irrational parameters of dwell force and frequency have been compared in the experiments. The typical defects of flash and accumulation can be eliminated by using the floating axial holder with optimal parameters.
Highlights
Plastic forming methods such as rolling, spinning and extrusion are superior to machining method in spline shaft manufacturing owing to the higher strength of products [1,2,3]
The material flow can be divided by three parts (figure 3 (a)), which are flowing to the tooth tip, accumulating with the die and against the forming direction
The products formed by the same frequency but different dwell forces were shown in figure 4
Summary
Plastic forming methods such as rolling, spinning and extrusion are superior to machining method in spline shaft manufacturing owing to the higher strength of products [1,2,3]. The material is forced to shaped parts through the dies which are exposed to high loads. Numerous studies have been done to find the reasons of force reduction in the oscillating forming process. Because the die goes in the opposite direction in the back step, reverse friction will cause the material to flow back. An axial holder is necessary to control the material flow. The effects of the axial holder are similar to the blank holder in deep drawing process which is usually used to guarantee stability and control friction force [12]. A floating axial holder with dwell force is designed to control the material flow in oscillating cold forging of spline shaft. The effects of dwell force on forming force, material flow and tooth shape were studied. Based on the results of simulation, the optimal value of dwell force have been found and verified in the experiments
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